This paper explores the fundamental semantic and syntactic properties of Japanese mimetic lexemes as iconic signs that depict various eventualities by means of linguistic sound. We argue how the two central features of mimetics&#160;&#8211; stem-based morphology and dynamicity&#160;&#8211; restrict their morphosyntactic and semantic realizations. The discussion on the impossible uses of mimetics, such as intrinsically static adjectival expressions and object-oriented depictives, particularly clarifies the limits of the traditional root-based analysis of mimetic morphology and sets the basis for its theoretical treatment.